Radiation heat exchanger for tube segments such as heating tubes in electrical impedance furnace

Abstract

The present disclosure includes an electrical impedance furnace for use in chemical production processes and methods of heating feedstock with an electric furnace of the invention. The electric furnace comprises a main heating section; a radiant heat exchanger section comprising an exchanger housing having first and second exchanger sidewalls; and a plurality of electrically conductive reactor tubes extending through the heater housing and the exchanger housing, each reactor tube defining a flow path and having a flanged connector at a respective end of the tube; and an electrical circuit configured to electrically connect the longitudinal portions of each of the reactor tubes in series, such that applying a voltage difference between the first end of the longitudinal portion of the first one of the reactor tubes and the second end of the longitudinal portion of the last one of the reactor tubes will cause current to sequentially flow through the longitudinal portions of all of the plurality of reactor tubes. In some such furnaces, the respective ends of the reactor tubes are electrically isolated from the electrically conductive feedstock and collection manifolds, e.g., by flanged conduit isolation joints. In some such furnaces, one or both of the exchanger sidewalls each define a channel configured to receive a fluid to absorb thermal energy from the respective exchanger sidewall. The inventive method comprises: heating the feedstock using one of the inventive furnaces by applying a voltage difference between a first end of a longitudinal portion of a first of the reactor tubes and a rearmost end of a longitudinal portion of a second of the reactor tubes to cause a current to sequentially flow through the longitudinal portions of all of the plurality of reactor tubes; wherein the voltage difference is greater than 100 volts (V); and wherein electrical current does not flow into either the collection manifold or the feedstock manifold.

Description

Technical Field

[0001] The present disclosure relates generally to industrial furnaces and, more particularly, but not by way of limitation, to radiant heat exchangers for tube segments, such as heating tubes in an impedance furnace. Background Art

[0002] Chemical synthesis equipment is used to provide a variety of chemicals.Usually, burning (burn) or burning (combust) special fuel is to provide the energy of reaction heat for chemical synthesis, the energy of heating one or more process streams, the energy of evaporating liquid (such as boiling water as diluent), the energy of doing work (such as driving compressor or pump) or the energy for other process operations in whole chemical synthesis equipment.This burning (burning) or burning (combustion) of fuel cause the generation of flue gas containing CO2, which can be harmful to the environment, and also cause the loss of energy efficiency of process.Similarly, steam is conventionally used as heat and / or energy transfer fluid of equipment range in chemical synthesis equipment.The steam for heat and / or energy transfer is often produced via the burning of fuel, causes during chemical synthesis, produces extra flue gas and further energy efficiency loss.

[0003] However, electrification of some components within chemical synthesis equipment presents additional issues and challenges. For example, in steam cracking processes, electrically heated pyrolysis furnaces can present issues or require consideration of factors that differ from, and / or are not necessarily present in, combustion-driven pyrolysis furnaces. As an example, impedance furnaces typically utilize an electric current flowing through the tube walls to heat the fluid flowing through the tubes, making the tubes both a conduit for the process and a conductive element for the electrical heating.

[0004] However, such impedance furnaces can be economically challenging because the energized tubes are connected to unenergized upstream and downstream piping and / or manifold systems. A conventional method for energizing the tubes in such an electric furnace is to configure the circuit so that a high voltage or potential is in the middle of each tube, and a low voltage or potential (e.g., very close to ground) is at each end of the tube (near the upstream / downstream connections). In this configuration, energizing the upstream / downstream piping is avoided by having the current flow into and out of the furnace tubes within the furnace itself. However, this arrangement allows each furnace tube to have its own circuit, and using conventional tube materials of construction (typically various high-alloy metals), the voltage drop across the circuit is very low—typically 10 volts (V) to 50 V. Summary of the Invention

[0005] Using a small voltage drop of 10V to 50V to deliver the heating load of a large industrial furnace (e.g., 10 megawatts (MW) - 250 MW (e.g., 100 MW)) requires enormous currents. For example, a 20 MW furnace would require 1,000,000 amperes at 20V, and its electrical equipment (e.g., step-down transformers, switchgear, thyristors, connection panels, copper conductors, and related components) can be prohibitively expensive. Furthermore, the complexity of the electrical equipment required for such large currents results in heat losses, which can make low-voltage impedance furnaces relatively inefficient. Therefore, higher voltages would help make impedance furnaces commercially viable.

[0006] One way to achieve higher voltages is to electrically isolate the furnace tubes from their upstream / downstream piping connections. With the heater tubes electrically isolated, a circuit can be configured with series-connected furnace tubes, allowing for much higher voltage drops, such as 480V, 4160V, or 13,200V (13.2kV), standard voltages already used (and therefore available) in industrial settings. At these higher voltages, the required current is correspondingly lower, as is the cost and complexity of the required electrical equipment. For example, a 20MW furnace requires only 4800 amps at 4160V (compared to 1,000,000 amps at 20V), significantly reducing the complexity and cost of the required electrical equipment relative to the much higher current and lower voltage required. Heat losses are also reduced, making high-voltage furnaces significantly more efficient.

[0007] Electrical isolation can be achieved through pipe isolation joints (PIJs), each of which mechanically couples the end of a conductive furnace tube to a conductive upstream or downstream pipe or manifold, where a sealed connection is established between the tube and the pipe / manifold's respective flow paths and does not allow electrical connection or current flow between the tubes / manifolds. For example, a dielectric or other electrically insulating material can be positioned between the tubes and the pipe / manifold to prevent physical contact between their respective materials. Different dielectric or other electrically insulating materials can be selected for different applications. For example, as temperature increases, at least some dielectrics will change in their dielectric properties, which can allow current to flow, such as at higher voltages. In other words, as temperature increases, the dielectric's ability to withstand a voltage difference without current flow decreases and eventually breaks down. In addition to appropriately selecting the dielectric material for the PIJ, other properties can also be selected to ensure the desired electrical isolation properties; for example, increasing the thickness of the dielectric material can increase the breakdown voltage at which the dielectric begins to allow current flow (and thus can increase the temperature at which the breakdown voltage drops below a desired threshold).

[0008] The present disclosure includes radiant heat exchangers for industrial-scale impedance furnaces (eg, for steam cracking, steam methane reforming, and / or various other applications) having pipe isolation joints that electrically isolate furnace tube sections and thereby enable the use of higher voltages and improved efficiency.

[0009] However, one challenge with using pipe isolation joints to electrically isolate pipe segments is that some dielectric materials typically exhibit a breakdown voltage, above which they begin to conduct current. The breakdown voltage of a particular material may also have an inverse relationship with temperature, meaning that at elevated temperatures, the breakdown voltage may decrease. Furthermore, some dielectric materials (e.g., electrically insulating polymers) exhibit physical changes (e.g., melting) at elevated temperatures. This melting can both destroy the insulating properties and allow undesirable leakage of liquid from the joint.

[0010] The tubes of an electrical impedance furnace require heating and elevated temperatures. However, in the configuration of the present invention, a portion of each tube (downstream of the actively heated portion of the tube) can be cooled after the contents of the tube have been heated sufficiently to carry out the desired chemical reaction. Even so, the current flowing longitudinally along each tube in the impedance furnace means that electrical connectivity between the respective tubes must be limited to prevent shorting of the heating circuit. Therefore, the outer portions of the heated tubes cannot be cooled in a common chamber with water or other conductive liquid, as doing so would cause the liquid to conduct electricity between the tubes. However, in the configuration of the present invention, the downstream portion of such tubes extends through one or more of the radiant heat exchangers of the present invention to reduce the temperature of such tubes between the main heating section of such furnace and the corresponding pipe isolation joint (PIJ), so that the maximum temperature to which the PIJ is exposed is limited to a range within which the material of the PIJ maintains its physical stability and / or electrical isolation properties.

[0011] In some configurations of an electric furnace for a chemical production process according to the present invention, the furnace comprises: a primary heating section; a radiant heat exchanger section; a plurality of electrically conductive reactor tubes; and an electrical circuit. In such configurations, the primary heating section comprises a heater housing having a first end, a second end, and first and second furnace sidewalls extending from the first end to the second end; the radiant heat exchanger section comprises an exchanger housing having a first exchanger end, a second exchanger end, and first and second exchanger sidewalls extending from the first exchanger end to the second exchanger end; the reactor tubes extend through the heater housing and the exchanger housing, wherein each of the reactor tubes defines a flow path from an inlet end of the reactor tube to an outlet end of the reactor tube, and each of the inlet end and the outlet end has a flanged connector; and the electrical circuit is configured to electrically connect longitudinal sections of each of the reactor tubes in series, such that applying a voltage difference between the first end of the longitudinal section of a first one of the reactor tubes and the second end of the longitudinal section of a last one of the reactor tubes causes current to flow sequentially through the longitudinal sections of all of the plurality of reactor tubes, wherein at least a majority of the longitudinal sections are disposed within the heater housing. In such a configuration, the radiant heat exchanger section is configured to, for each of the reactor tubes, reduce the temperature of the outlet end of the tube relative to the nearest first or second end of the longitudinal portion of the tube.

[0012] In some configurations of the inventive furnace, the inlet end of the reactor tube is disposed on the first end of the heater shell, and the outlet end of the reactor tube is disposed on the second end of the exchanger shell.

[0013] In some configurations of the inventive furnace, the inlet and outlet ends of the reactor tubes are disposed on the second end of the exchanger housing, and each reactor tube includes a U-shaped portion at the first end of the heater housing.

[0014] In some configurations of the inventive furnace, the plurality of reactor tubes includes a first subset of reactor tubes disposed with their inlet ends on the first end of the heater housing and their outlet ends on the second end of the exchanger housing, and a second subset of reactor tubes disposed with their outlet ends on the first end of the heater housing and their inlet ends on the second end of the exchanger housing.

[0015] In some configurations of the inventive furnace, an electrical circuit connects the second end of the longitudinal section of a first one of the reactor tubes with the first end of the longitudinal section of a second one of the reactor tubes, and connects the second end of the longitudinal section of the second one of the reactor tubes with the first end of the longitudinal section of a third one of the reactor tubes.

[0016] In some configurations of the present invention furnace, (a) the first exchanger sidewall defines a channel configured to receive a fluid to absorb heat energy from the first exchanger sidewall; (b) the second exchanger sidewall defines a channel configured to receive a fluid to absorb heat energy from the second exchanger sidewall; or (c) both (a) and (b). In some such configurations, an outlet of each channel is coupled in fluid communication to a steam drum.

[0017] Some configurations of the present furnace further include a catalyst disposed in the reactor tube, wherein the catalyst is a steam reforming catalyst configured to react steam and methane gas to form hydrogen and carbon monoxide.

[0018] In some configurations of the furnace of the present invention, (a) the outlet end of the reactor tube is coupled to a conductive collection manifold, and wherein the reactor tube is electrically isolated from the collection manifold; (b) the inlet end of the reactor tube is coupled to a conductive feed manifold, and wherein the reactor tube is electrically isolated from the feed manifold; or (c) both (a) and (b). In some such configurations, electrical isolation of each reactor tube is provided by one or more flanged pipe isolation joints (PIJs).

[0019] Some embodiments of the present methods include: heating the feedstock using one of the configurations of the present furnace by applying a voltage differential between a first end of a longitudinal section of a first one of the reactor tubes and a last end of a longitudinal section of a second one of the reactor tubes to cause current to flow sequentially through the longitudinal sections of all of the plurality of reactor tubes; wherein the voltage differential is greater than 100 volts (V); and wherein the current does not flow into either the collection manifold or the feedstock manifold.

[0020] In some embodiments of the present methods, the furnace is part of a steam methane reformer (SMR) system and the feedstock comprises steam and methane.

[0021] In some embodiments of the present method, the furnace is part of a steam cracking system and the feed comprises steam and at least one component selected from the following list of components: naphtha, liquefied petroleum gas (LPG), and ethane.

[0022] Some embodiments of the present method further include: flowing the H2O through the channels in the sidewall of the exchanger to absorb heat energy from the sidewall of the exchanger. Some such embodiments further include: passing the H2O from the channels in the sidewall of the exchanger to a steam drum to separate liquid and steam from the H2O.

[0023] The term "coupled" is defined as connected, although not necessarily directly, and not necessarily mechanically; two items that are "coupled" can be integral with each other. Unless otherwise expressly required by the present disclosure, the terms "a" and "an" are defined as one or more. As understood by one of ordinary skill in the art, the term "substantially" is defined as being largely, but not necessarily completely, what is specified (and includes what is specified; for example, substantially 90 degrees includes 90 degrees, and substantially parallel includes parallel). In any embodiment of the apparatus, kit, and method of the present invention, the term "substantially" can be replaced with "within [percentage] of what is specified," where percentages include 0.1%, 1%, 5%, and / or 10%.

[0024] The terms "comprise" (and any form of comprising, such as "comprises" and "comprising"), "have" (and any form of having, such as "has" and "having"), "include" (and any form of including, such as "includes" and "including"), and "contain" (and any form of containing, such as "contains" and "containing") are open-ended linking verbs. Thus, a device or set that "comprises," "has," "includes," or "contains" one or more elements possesses those one or more elements, but is not limited to possessing only those elements. Similarly, a method that "comprises," "has," "includes," or "contains" one or more steps possesses those one or more steps, but is not limited to possessing only those one or more steps.

[0025] Further, an apparatus, device, or system that is configured in some way is configured in at least that way, but it may also be configured in other ways besides those specifically described.

[0026] Any embodiment of any of the present apparatus and methods may consist of or consist essentially of any of the described steps, elements, and / or features, rather than comprising / including / containing / having any of the described steps, elements, and / or features. Thus, in any claim, the term "consisting of" or "consisting essentially of" may replace any of the above recited open-ended linking verbs in order to alter the scope of a given claim from that which would otherwise be used.

[0027] Details and others associated with the above-described embodiments are presented below.

[0028] Some details associated with aspects of the present disclosure are described above, and others are described below. Other implementations, advantages, and features of the present disclosure will become apparent after reviewing the entire application (including the accompanying drawings, detailed description, and claims). BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The following figures illustrate by way of example and not limitation. For the sake of brevity and clarity, not every feature of a given structure is labeled in every figure in which that structure appears. The same reference numeral or reference numeral does not necessarily indicate the same structure. On the contrary, the same reference numeral may be used to indicate similar features or features having similar functions, as may different reference numerals. Dimensional drawings are drawn to scale (unless otherwise indicated), meaning that the sizes of the depicted elements are accurate relative to each other for at least the embodiments depicted in the figures.

[0030] Figure 1 A flow diagram describing a general methanol synthesis plant or process.

[0031] Figure 2 Description can be configured as Figure 1 Block diagram of an electrical impedance furnace used in the syngas synthesis section of an apparatus or process.

[0032] Figure 3 Description used in Figure 2 Conceptual diagram of a first example of an impedance furnace used in a pyrolysis reaction section.

[0033] Figure 4 Describes the use of a Figure 3 A cross-sectional side view of a first example of a pipe isolation joint of the present invention used in an example of FIG.

[0034] Figure 5 Description and Figure 4 Plan view of the isolation disc used with the pipe isolation joint.

[0035] Figure 6A Description used in Figure 2 Conceptual diagram of a second example of an impedance furnace with two radiant heat exchangers used in the pyrolysis reaction section.

[0036] Figure 6B Description along the lines of Figure 6A The line 6B-6B is intercepted Figure 6A A cross-sectional view of one of the radiation heat exchangers.

[0037] Figure 7A Description used in Figure 2 Conceptual diagram of a third example of an impedance furnace with a radiant heat exchanger used in a pyrolysis reaction section.

[0038] Figure 7B Description along the lines of Figure 7A The line 7B-7B intercepts Figure 7A Cross-section of a radiation heat exchanger. DETAILED DESCRIPTION

[0039] Referring now to the drawings, and more particularly to the Figure 1 , a flow diagram of an example of a general methanol synthesis plant is shown, which includes one or more of the following process sections for converting a feed stream 5 into a methanol product stream 45 (and optionally one or more by-product streams 41): a feed pretreatment section 10, a syngas synthesis section 20, a methanol synthesis section 30, a methanol purification section 40, or a combination thereof. Such sections will be briefly described in the next few paragraphs and described in more detail below.

[0040] As indicated in the methanol synthesis flow diagram, the feed pretreatment section 10 of the methanol synthesis plant is operable to prepare (e.g., remove undesirable components (e.g., sulfur) from the feed 5, adjust the temperature and / or pressure of the feed 5) the feed 5 for reforming, thereby providing a pretreated feed 15. In some applications, the methanol synthesis plant of the present disclosure does not include a feed pretreatment section. The syngas synthesis section 20 is operable to produce syngas from the feed 5 or the pretreated feed 15 to produce a syngas synthesis product 25 comprising carbon monoxide (CO) and hydrogen (H2).

[0041] In some embodiments, the syngas generation section 20 is a syngas synthesis section that is operable to steam reform a feed (e.g., feed 5 comprising natural gas or pretreated feed 15) to produce a reformer product comprising carbon monoxide (CO) and hydrogen (H2). The syngas synthesis (or "reformer") product 25 may also include carbon dioxide (CO2), water, methane (CH4), and / or impurities. For example, some embodiments of the electric furnace of the present invention may include a steam reforming catalyst to perform a syngas reaction to produce carbon monoxide and hydrogen.

[0042] The methanol synthesis section 30 is operable to produce methanol from the syngas synthesis product 25 and thereby provide a crude methanol stream 35. The methanol purification section 40 is operable to separate a purified methanol product 45 and by-products 41 from the crude methanol stream 35.

[0043] Now refer to Figure 2 , shows that it can be configured as Figure 1 A block diagram of an electrical impedance heater 100 for use in the syngas synthesis (steam reforming) section 20 of an apparatus or process. Figure 2 As shown in , the furnace generally includes a fluid inlet 104 and a fluid outlet 108 .

[0044] Figure 1 and Figure 2 An example of a methanol synthesis system is described for illustrative purposes, but the electrical impedance furnace of the present invention may be used in any of a variety of chemical synthesis systems and processes, particularly in place of furnaces historically driven by direct combustion or fossil fuels.

[0045] Now refer to Figure 3, shown for the Figure 2 A conceptual diagram of a first embodiment of an impedance furnace 100a for use in a pyrolysis reaction (20) section of a device. In this configuration, the furnace 100a includes a housing 112 and a plurality of furnace tubes 116 extending through the housing. Each tube 116 includes a sidewall 120 defining a flow passage extending from an inlet end 124 to an outlet end 128, and each tube includes a flange 132.

[0046] In the depicted configuration, the furnace 100a is coupled to first and second inlet manifolds 136a, 136b, and first and second outlet manifolds 140a, 140b. Specifically, the inlet ends 124 of the tubes 116 are each coupled to a respective one of the inlet manifolds 136a, 136b; and the outlet ends 128 of the tubes 116 are each coupled to a respective one of the outlet manifolds 140a, 140b. Each inlet manifold 136a, 136b includes a plurality of connectors having flanges 144 that are coupled to a respective flange 132 via pipe isolating fittings 148 at the inlet ends 124 of the tubes 116; and each outlet manifold 140a, 140b includes a plurality of connectors having flanges 144 that are coupled to a respective flange 132 via pipe isolating fittings 148 at the outlet ends 128 of the tubes 116. As described in more detail below, the tube isolation joints 148 electrically isolate the furnace tubes 116 from the manifolds ( 136a , 136b , 140a , 140b ) and, thus, prevent electrical current from flowing between the tubes and the manifolds.

[0047] Because the furnace tubes 116 are electrically isolated from the manifolds (136a, 136b, 140a, 140b), an electrical potential can be applied across multiple furnace tubes connected in series. For example, in the configuration depicted (which includes a relatively small number of tubes 116 for illustrative purposes), the tubes are electrically connected in series to apply a voltage difference across all of the tubes in series, such that the voltage difference applied across the tubes causes current to flow sequentially through each tube. In particular, point 156a closer to the outlet end 128 of the first tube 116a is electrically connected to point 152b closer to the inlet end 124 of the second tube 116b, point 156b closer to the outlet end 128 of the second tube 116b is electrically connected to point 152c closer to the inlet end 124 of the third tube 116c, point 156c closer to the outlet end 128 of the third tube 116c is electrically connected to point 152d closer to the inlet end of the fourth tube 116d, point 156d closer to the outlet end 128 of the fourth tube 116d is electrically connected to point 152e closer to the inlet end 124 of the fifth tube 116e, and point 156e closer to the outlet end 128 of the fifth tube 116e is electrically connected to point 152f closer to the inlet end 124 of the sixth tube 116f. Thus, when a voltage difference is applied across the furnace tubes (116), with a high potential (indicated by a + circle) at point 152a closer to the inlet end 124 of the first tube 116a and a low potential (indicated by a - circle) at point 156f closer to the outlet end 128 of the sixth tube 116f, current flows sequentially through points 152a, 156a, 152b, 156b, 152c, 156c, 152d, 156d, 152e, 156e, 152f, and 156f, as indicated by the dashed arrows next to the tubes (116). In this configuration, both points 152 and 156 are located within the furnace shell (112), such that substantially all of the current flowing along the tubes (116) remains within the furnace shell.

[0048] While a small number of furnace tubes 116 are shown for illustrative purposes, an industrial furnace will typically include a much larger number of tubes through which fluid can flow and be heated, such that the voltage drop along each tube will typically be around 50V. For example, a furnace with a voltage drop of 4160V across all tubes 116 and eighty (80) furnace tubes 116 will exhibit an average voltage drop of approximately 50V per tube. Thus, the electrical isolation of the tubes 116 from upstream and downstream piping or manifolds (e.g., 136a, 136b, 140a, 140b) and the resulting ability to connect the tubes sequentially allow for a much larger overall voltage drop, thereby significantly reducing the current required to generate a heating load sufficient for industrial applications. For example, a 20 MW impedance heater at 4160V would require only 4800 amps (compared to 1 million amps for a similar heater at only 20V).

[0049] Now refer to Figure 4 and Figure 5 , Figure 4 depicts a cross-sectional side view of a first embodiment 148a of a pipe isolation joint of the present invention for use in an impedance furnace (e.g., furnace 100a), and Figure 5 A plan view of an isolation disc for use with pipe isolation fitting 148a is depicted. In the depicted configuration, pipe isolation fitting 148a is an assembly comprising conductive first flange 132, conductive second flange 144, isolation disc 200, a plurality of fastener isolators 204, one or more isolation sleeves 208, and one or more fastener assemblies 212.

[0050] The flange 132 defines a first opening 216, and the flange 144 defines a second opening 220 that is configured to align with the first opening 216 as shown. In the depicted configuration, the flange 132 defines a plurality of first openings 216 that surround a primary first passage 224 (similar to Figure 5 The insulating disc 142 is provided on the outer surface of the second flange 144, and the second flange 144 defines a plurality of second openings 220 surrounding the main second passage 228 so that the passage 228 is configured to be aligned with the passage 224, and each of the second openings 220 is configured to be aligned with a corresponding one of the first openings 216.

[0051] The isolating disk 200 comprises a non-conductive material and defines one or more disk openings 240. For example, in the depicted example, the isolating disk 200 defines a primary disk passage 236 and a plurality of disk openings 240 that surround the primary disk passage 236 and are spaced apart from one another (e.g., at equal angular intervals) such that the primary disk passage 236 is configured to align with the primary first and second passages 224, 228, and the disk openings 240 are configured to align with a respective one of the first and second openings 216, 220. The primary disk passage 236 and the primary first and second passages 224, 228 (and their respective tubes or pipes) can have an inner diameter of 1 to 10 inches (e.g., between any two of 1, 2, 3, 4, 5, 6, 7, 8, 9, and / or 10 inches). For example, in some configurations, such an inner diameter is between 1 and 3 inches, and in other configurations, between 5 and 7 inches.

[0052] Each fastener isolator 204 comprises a non-conductive material and defines one or more fastener holes 244. For example, in the depicted configuration, each fastener isolator 204 has a conventional washer shape to define a single fastener hole 244; however, in other configurations, each fastener isolator 204 may be shaped as a disk to define multiple fastener holes, similar to Figure 5 Isolation plate.

[0053] Each isolation sleeve 208 comprises a non-conductive material and defines an internal fastener passage 248. Figure 4 As shown in , each isolating sleeve 208 has an outer profile configured to extend through the first opening 216 of the flange 132 and the corresponding second opening 220 of the flange 144 and into (eg, through) the disk opening 240 of the isolating disk 200 .

[0054] Each fastener assembly 212 includes a longitudinal medial portion 252 and first and second retaining portions 256, with each retaining portion having a transverse dimension 260 that is greater than the corresponding transverse dimension 264 of the medial portion. In at least some configurations, each fastener assembly 212 comprises a conductive material, such as steel or another metal alloy. In the depicted configuration, each fastener assembly comprises a threaded stud 268, with a nut 272 threaded onto opposite ends of the stud, as shown. In other configurations, each fastener assembly may have any configuration that allows for the described functionality. For example, in other configurations, each fastener assembly may include a bolt with an enlarged head on one end and a nut 272 threaded onto the opposite end.

[0055] like Figure 4 As shown in FIG, flange 132 is configured to be coupled to flange 144 with isolating disc 200 between the flanges. In use, each isolating sleeve 208 extends through first opening 216 of flange 132, through corresponding second opening 120 of flange 144, and into (e.g., through) corresponding disc opening 240. A corresponding fastener assembly 212 also extends through the isolating sleeve (208), with one of the fastener isolators (204) disposed between first retaining portion 256 and flange 132, and another of the fastener isolators (204) disposed between second retaining portion 256 and flange 148.

[0056] As shown, isolation disk 200 , isolation sleeve 208 , and fastener isolation body 204 are configured so that once assembled, they prevent fastener components from contacting either flange and prevent flanges 132 , 144 from contacting each other, thereby electrically isolating flange 132 from flange 144 .

[0057] The non-conductive material of each of the insulating disc 200, insulating sleeve 208, and fastener insulator 204 is selected to remain solid and non-conductive at the desired operating temperature and voltage, for example, at voltages up to 200 V and temperatures up to 300° C. In some configurations, the non-conductive material of the insulating disc 200, insulating sleeve 208, and / or fastener insulator is selected to remain solid and non-conductive at voltages greater than 100 V (e.g., greater than any one or any two of the following: 100 V, 200 V, 300 V, 400 V, 500 V, 600 V, 700 V, 800 V, 900 V, and / or 1000 V) and temperatures exceeding 300° C. (e.g., greater than any one or any two of the following: 300° C., 400° C., 500° C., 600° C., or greater). In some embodiments, such as those where the isolation disk is particularly rigid and sufficiently resistant to deformation under pressure to seal the interface, additional sealant (which does not need to be electrically insulating) is added between the isolation disk 200 and the corresponding flange (132, 144).

[0058] Various polymers (e.g., polyetherimide (PEI)), copolymers (e.g., PEI copolymers), and ceramics (e.g., alumina, zirconia, silicon nitride, tricalcium phosphate, and silicon-based materials) can be configured to exhibit these properties and be sufficiently formable (e.g., via molding, machining, and / or other methods) to provide at least some of the shapes described herein for use in insulating disks, insulating sleeves, and fastener insulators. Some such non-conductive materials (e.g., polymers) can exhibit physical changes (e.g., melting) with elevated temperatures (around 300°C to 400°C). For example, some PEIs exhibit melting temperatures as high as 340°C to 360°C. Thus, as long as the PEI is chemically stable in the presence of the fluids to which it will be exposed, the PEI can be a suitable non-conductive material for desired operating temperatures around 250°C or 275°C. Other materials (e.g., polymers) remain electrically insulating and dimensionally stable at higher temperatures (e.g., around 500°C, 550°C, or even 600°C or higher).

[0059] For voltages of approximately 100V and greater (e.g., 1000V) across the pipe isolation joint, the minimum thickness of the non-conductive material of the isolation disk (200), fastener insulator (204), and isolation sleeve 208 (e.g., the vertical thickness of each of the isolation disk (200) and fastener insulator (204), and the horizontal thickness of the sidewall of the isolation sleeve) can be 0.15 inches or greater (e.g., greater than any one of or between any two of the following: 0.15 inches, 0.20 inches, 0.25 inches, 0.30 inches, 0.35 inches, 0.40 inches, 0.45 inches, 0.50 inches, or greater). In some configurations, the thickness of the isolation disk is greater than the thickness of each fastener insulator (204) and / or greater than the thickness of the sidewall of the isolation sleeve (208). For example, in some configurations, the fastener insulator (204) and the insulation sleeve (208) each have a first minimum thickness (e.g., greater than any one or between any two of: 0.15 inches, 0.20 inches, 0.25 inches, 0.30 inches, 0.35 inches, 0.40 inches, 0.45 inches, 0.50 inches, or more); and the isolation disc (200) has a second minimum thickness greater than the first minimum thickness (e.g., greater than any one or between any two of: 0.20 inches, 0.25 inches, 0.30 inches, 0.35 inches, 0.40 inches, 0.45 inches, 0.50 inches, or more). By way of specific example, in one such configuration, the first minimum thickness is 0.25 inches, and the second minimum thickness is 0.5 inches. In addition to directly preventing contact between conductive surfaces, the configuration of the isolating disk (200) and the isolating sleeve (208) also ensures spacing between the conductive surfaces, and the isolating disk (200) and the isolating sleeve (208) can be configured to ensure sufficient minimum spacing (air gap) to avoid arcing between portions of the conductive surfaces that are not directly separated or interposed by a portion of either the isolating disk (200) or the isolating sleeve (208).

[0060] Now refer to Figure 6A and 6B , Figure 6A A conceptual diagram depicting a second embodiment of an impedance furnace 100b having two radiant heat exchangers 300a, 300b for heating the Figure 2 used in the pyrolysis reaction section (20); and Figure 6B describe Figure 6A The furnace 100b is similar in many respects to the radiant heat exchanger 300a of FIG. Figure 3 For example, as described above with reference to Figure 3As explained for furnace 100a in the above, furnace 100b includes circuitry configured to electrically connect the longitudinal sections (between 152, 156) of each of the reactor tubes (116) in series such that applying a voltage difference between a first end 152a of the longitudinal section of a first one of the reactor tubes 116a and a second end 156f of the longitudinal section of a last one of the reactor tubes 116f causes current to flow sequentially through the longitudinal sections of all of the plurality of reactor tubes, wherein at least a majority (e.g., all as shown) of the longitudinal sections are disposed in heater housing (112).

[0061] However, furnace 100b also differs from furnace 100a in that the furnace shell 112 of furnace 100b includes a first radiant heat exchanger 300a at a first end 304 of the furnace shell 112 and a second radiant heat exchanger 300b at an opposite second end 308 of the furnace shell 112. The furnace sidewall 312 extends from the first end 304 to the second end 308 as shown. In this configuration, each radiant heat exchanger section 300a, 300b is configured to, for each of the reactor tubes, reduce the temperature of the outlet end (128) of the tube relative to the nearest first or second end of the longitudinal portion of the tube (e.g., 156b). As described above in the Summary of the Invention, the reduction in the temperature of the tube near the flange 132 at the outlet end (128) of the tube (relative to the temperature of the hot side of the tube when it exits the furnace shell 112) can maintain the physical stability and electrical isolation properties of the material in the corresponding pipe isolation joint (PIJ) 148.

[0062] The first radiant heat exchanger 300a includes an exchanger housing 316 having an exchanger first end 320a, an exchanger second end 324a, and first and second exchanger sidewalls 328a, 328b extending a length 332a from the first end 320a to the second end 324a. Figure 6B Similarly, the second radiant heat exchanger 300b includes an exchanger housing 316b having an exchanger first end 320b, an exchanger second end 324b, and first and second exchanger sidewalls 328a, 328b extending a length 332b from the first end 320b to the second end 324b (similar to Figure 6B 300a). In the depicted embodiment, tube 116 traverses length 336 within furnace shell (112). Figure 6B As shown in FIG, tubes 116a-116f are arranged in two rows such that the tubes do not touch each other within the exchanger and are spaced apart from each other by substantially equal distances 340. In other configurations, the tubes may be arranged in a single row or in more than two rows.

[0063] In the depicted embodiment, the furnace sidewalls 312 comprise a material having a relatively high emissivity (e.g., 0.5 or greater, 0.7 or greater, or 0.8 or greater), such as any of a variety of metal alloys. In some configurations, at least some of the interior surfaces of the sidewalls 312, and / or at least some of the exterior surfaces of the tubes 116 in the exchangers 300a and 300b, are polished, coated, or both to increase the emissivity. The relatively high emissivity of the sidewalls 312 contributes to the sidewalls' ability to absorb thermal radiation from and emit thermal radiation to the tubes 116 within each radiant heat exchanger. For example, as Figure 6B As described in

[0014] , the configuration described includes furnace reactor tubes with flow in alternating directions. Additionally, due to the net absorption of thermal radiation, the average temperature of the exchanger sidewalls (312) will generally increase. Therefore, to further increase the net cooling of the tubes carrying heated fluid away from the furnace shell (112), in some configurations, the material of the furnace sidewalls 312 is also selected to have a relatively high specific heat capacity (e.g., 400 J / kg-K or greater, 450 J / kg-K or greater, or 500 J / kg-K or greater) to increase the amount of thermal energy that the sidewalls (312) themselves can temporarily "hold" as the thermal energy is dissipated.

[0064] exist Figure 6B In the direction of the furnace shell (112), the tubes with downward fluid flow carry fluid that has been heated in the furnace shell (112) and is being carried away from the furnace shell (112), while the tubes with upward fluid flow carry fluid that has not been heated and is being carried toward the furnace shell (112). Figure 6B In the radiant heat exchanger 300a, the "down" tubes are generally the hotter heat radiation emitters, the "up" tubes are generally the cooler heat radiation absorbers, and portions of the sidewall 312 can absorb and emit heat radiation depending on the temperature and position relative to the tubes. Although the radiant heat exchange is complex, the net effect of this configuration is to reduce the temperature of the "down" tubes as the distance from the furnace shell (112) increases, thereby reducing the temperature of the fluid flowing in the "down" tubes as the fluid flows away from the furnace shell (112); and to increase the temperature of the "up" tubes as the distance from the furnace shell (112) decreases, thereby increasing the temperature of the fluid flowing in the "up" tubes as the fluid flows toward the furnace shell (112). In operation, the radiant heat exchangers 300a, 300b extract thermal energy in the form of thermal radiation from the "hot" fluid leaving the furnace and use this thermal energy to preheat the "cold" fluid (as the "cold" fluid flows toward the furnace).

[0065] Several parameters can be varied to affect the degree of cooling experienced by the "hot" pipes as they extend from the furnace shell to the distal end of the respective heat exchangers. For example, for radiant heat exchanger 300a, the length 332a of exchanger 300a can be increased to increase cooling of the "hot" pipes (116a, 116c, 116e), and / or the temperature of the "cold" pipes 116b, 116d, 116f at the second end 328a of the exchanger can be reduced to increase the degree of cooling experienced by the "hot" pipes (116a, 116c, 116d). Furnace 100b was modeled for a steam-methane reforming (SMR) process, with a length 336 of 13 meters (m), and lengths 332a and 332b each equal to 5 meters. The "cold" gas inlet temperature at the outer ends of the heat exchangers (300a, 300b) is 650° C., while the "hot" gas leaving the furnace is at a temperature of 875° C. The temperature of the "hot" gas at the outer ends (324a, 324b) of the respective radiant heat exchangers 300a, 300b decreases from 875° C. to 848° C., while the temperature of the "cold" gas at the inner ends (320a, 320b) of the respective heat exchangers 300a, 300b increases from 650° C. to 674° C. As a result, the temperature at the inner diameter (ID) of the "hot" tube (i.e., the highest temperature along the thickness of the tube wall) decreases from 866° C. at the inner ends (320a, 320b) of the heat exchangers (which would be the temperature closest to the "hot" tube PIJ 148 in the absence of the radiant heat exchanger of the present invention) to 788° C. at the outer ends (324a, 324b) of the heat exchangers.

[0066] With the lengths 332a and 332b each increased from 5 meters to 10 meters, and all other conditions being equal, the temperature of the "hot" gas at the outer ends (324a, 324b) of the respective radiant heat exchangers 300a, 300b decreased from 875° C. to 820° C., while the temperature of the "cold" gas at the inner ends (320a, 320b) of the respective heat exchangers 300a, 300b increased from 650° C. to 699° C. As a result, the temperature at the inner diameter (ID) of the "hot" pipe (i.e., the highest temperature along the thickness of the pipe wall) decreased from 866° C. at the inner ends (320a, 320b) of the heat exchangers (which would be the temperature closest to the "hot" pipe PIJ 148 in the absence of the radiant heat exchangers of the present invention) to 770° C. at the outer ends (324a, 324b) of the heat exchangers.

[0067] With lengths 332a and 332b each equal to 10 meters, the system was modeled for a "cold" gas inlet temperature of 450° C. at the outer ends of the heat exchangers (300a, 300b). With this option, the temperature of the "hot" gas at the outer ends (324a, 324b) of the respective radiant heat exchangers 300a, 300b dropped from 875° C. to 811° C., while the temperature of the "cold" gas at the inner ends (320a, 320b) of the respective heat exchangers 300a, 300b increased from 450° C. to 552° C. As a result, the temperature at the inner diameter (ID) of the "hot" pipe (i.e., the highest temperature along the thickness of the pipe wall) dropped from 866° C. at the inner ends (320a, 320b) of the heat exchangers (which would be the temperature closest to the "hot" pipe PIJ 148 in the absence of the radiant heat exchanger of the present invention) to 695° C. at the outer ends (324a, 324b) of the heat exchangers.

[0068] If the lengths 332a and 332b are each equal to 10 meters, the system is modeled for a "cold" gas inlet temperature of 200°C at the outer ends of the heat exchangers (300a, 300b). In this case, the temperature of the "hot" gas at the outer ends (324a, 324b) of the respective radiant heat exchangers 300a, 300b decreases from 875°C to 721°C, while the temperature of the "cold" gas at the inner ends (320a, 320b) of the respective heat exchangers 300a, 300b increases from 200°C to 341°C. As a result, the temperature at the inner diameter (ID) of the "hot" pipe (i.e., the highest temperature along the thickness of the pipe wall) decreases from 866°C at the inner ends (320a, 320b) of the heat exchangers (which would be the temperature closest to the "hot" pipe PIJ 148 in the absence of the radiant heat exchanger of the present invention) to 630°C at the outer ends (324a, 324b) of the heat exchangers.

[0069] In general, while increasing the length of the radiant heat exchanger (332a, 332b) can reduce the tube temperature at the outer ends (324a, 324b) of the radiant heat exchanger (and thus for the "hot" tube PIJ 148), reducing the inlet temperature of the "cold" gas has a greater effect on reducing the tube temperature at the outer ends (324a, 324b) of the radiant heat exchanger (and thus for the "hot" tube PIJ 148). And while the configuration described may be applicable to SMR, and even preferred for other processes, it is generally desirable for SMR processes to have a higher "cold" gas inlet temperature so that Figure 7A and 7B Additional configurations may be preferred for at least some embodiments of the SMR process.

[0070] Now refer to Figure 7A and 7B , Figure 7A Description used in Figure 2A conceptual diagram of a third example of an impedance furnace 100c and a radiation heat exchanger 300c used in the pyrolysis reaction section (20); and Figure 7B Description of the intercept along route 7B-7B Figure 7A The furnace 100c is similar in many respects to the Figures 6A-6B For example, as explained above for furnace 100b, furnace 100c includes circuitry configured to electrically connect the longitudinal sections (between 152, 156) of each of the reactor tubes (116) in series such that applying a voltage difference between a first end 152a of the longitudinal section of a first one of the reactor tubes 116a and a second end 156f of the longitudinal section of a last one of the reactor tubes 116f causes current to flow sequentially through the longitudinal sections of all of the plurality of reactor tubes, wherein at least a majority (e.g., all as shown) of the longitudinal sections are disposed in heater housing (112).

[0071] However, furnace 100c also differs from furnace 100b in that the fluid flows through furnace housing 312 in a common direction (instead of alternating directions as in furnace 100b), such that first end 304 is the "cold" end and second end 308 is the "hot" end, and furnace 100c includes one radiant heat exchanger 300c on the hot end (308), as opposed to two radiant heaters on opposite ends as in furnace 100b. Thus, first ends 124 of all tubes (116a, 116b, 116c, 116d, 116e, 116f) are connected to a common inlet manifold 136, and second ends 128 of the tubes are connected to a common outlet manifold 140, such that the fluid flows through all tubes in the same direction (downward in the depicted direction). Additionally, as Figure 7B As shown, the tubes 116 of the furnace 100c are arranged in a row within the exchanger housing 316a.

[0072] In the depicted configuration, the housing 316a has an exchanger first end 320c, an exchanger second end 324c, and first and second exchanger sidewalls 328c, 328d extending a length 332c from the first end 320c to the second end 324c. Figure 6B In the depicted embodiment, the tube 116 traverses a length 336 within the furnace shell (112). Figure 6B As shown in FIG, the tubes 116a-116f are arranged in two rows such that the tubes do not touch each other within the exchanger and are spaced apart from each other by substantially equal distances 340a. In other configurations, the tubes may be arranged in multiple rows.

[0073] In addition, to promote radiative cooling of the tubes in exchanger 300c, each of the sidewalls 328c, 328d defines a channel 344 configured to receive a fluid to absorb thermal energy from the first exchanger sidewall. More particularly, each sidewall 328c, 328d includes an inner wall 348 and an outer wall 352 to define a substantially hollow interior that defines the channel 344. In the described embodiment, the inner wall 348 comprises a material having a relatively high emissivity (e.g., 0.5 or greater, 0.7 or greater, or 0.8 or greater), such as any of various metal alloys. In some configurations, at least some of the inner surfaces of the inner wall 348, and / or at least some of the outer surfaces of the tubes 116 in exchanger 300c, are polished, coated, or both to increase emissivity. The relatively high emissivity of the inner wall 348 contributes to the ability of the sidewall to absorb thermal radiation from the tubes 116 in each radiant heat exchanger and to emit thermal radiation to the tubes 116 in each radiant heat exchanger. Without cooling by the fluid within the channels 344, the average temperature of the exchanger sidewalls (312) would generally increase due to the net absorption of thermal radiation. Ideally, the material of each inner sidewall 348 is selected to have a relatively high emissivity for effectively absorbing thermal radiation from the tubes (116) on the inner surface of the inner wall 348, and a relatively high conductivity for effectively transferring thermal energy through its outer surface to the cooling fluid within the channels 344.

[0074] An inlet 356 is coupled to a first side of the housing 316a such that the inlet is in fluid communication with the passage, and an outlet 360 is coupled to a second side of the housing 316b such that the outlet is in fluid communication with the passage. Thus, a source of cooling fluid can be coupled to the inlet 356 such that the cooling fluid flows through the passage and out of the outlet 360. When delivered to the inlet 356 at a lower temperature than the inner wall 348, such cooling fluid can directly absorb thermal energy from the inner wall 348 and thereby lower the temperature of the inner wall 348, thereby increasing its absorption of radiant heat from the tubes 116 and increasing radiative cooling of the tubes (relative to the plate walls in the furnace 100b that are not cooled by additional fluid).

[0075] In a specific example of a cooling fluid, fluid HO (e.g., boiler feed water (BFW)), can be delivered in a liquid state or in a two-phase state (containing some liquid and some steam). As the fluid HO flows through the channel 344, all or some of it can be converted to steam before reaching the outlet 360. When a portion of the fluid HO remains in a liquid state, the outlet 360 can be coupled to a steam drum 364 to separate the liquid portion from the gaseous portion, and, for example, the liquid portion can be recycled to the inlet 356 and / or the steam portion can be redirected to recover heat energy elsewhere (e.g., to preheat the feed to the reactor tubes 116).

[0076] For the steam methane reforming (SMR) process, Figure 7A and 7BA configuration was modeled in which the gas in tube 116 enters the exchanger housing 316a at end 320c at a temperature of 850°C, wherein boiler feed water (BFW) is delivered in liquid form to inlet 356 at a flow rate at which a portion of the BFW evaporates within the channels 344 of the side walls 328c, 328d at a typical steam pressure of 600 psi and an inner wall 348 temperature of 274°C. Modeling was performed for different heat exchanger lengths 332c, specifically 20 meters, 14 meters, and 10 meters. The results are shown in Table 1. The "corner tubes" refer to the tubes at the leftmost and rightmost positions, respectively, in the exchanger 300c (see FIG. 1 ). Figure 7B ), the tubes experience higher temperatures due to having a "view" of a smaller portion of the exchanger sidewall.

[0077] Table 1

[0078]

[0079] As shown in Table 1, flowing cooling fluid through the channels (344) of heat exchanger 300c resulted in a significantly greater decrease in the temperature of the tubes (116) along the heat exchanger length 332c and in the tubes (116) (relative to exchangers 300a, 300b).

[0080] While radiant heat exchanger 300c includes two hollow sidewalls 328c, 328d, each defining one or more channels 344, other configurations of the radiant heat exchanger of the present invention may include only a single hollow sidewall defining one or more channels for the cooling fluid. For example, in other configurations of furnace 100a, the reactor tubes may be U-shaped, such that the inlet and outlet ends of each tube are located at the same end of the furnace. In such a configuration, the "cold" side of all U-shaped tubes may be located on a first side of the heat exchanger, and the "hot" side of all U-shaped tubes may be located on an opposite second side of the heat exchanger, with the hollow sidewalls located on the same side as the "hot" sides of the tubes. In such a configuration, fluid flow through the hollow sidewalls can increase the degree of radiative cooling on the "hot" side of the tubes, while also allowing for a higher inlet temperature on the "cold" side of the tubes, which still receives some degree of radiative preheating from the "hot" side of the tubes.

[0081] ***

[0082] Additional details regarding various components of the syngas synthesis apparatus and process can be found in International Patent Application Publication No. WO 2020 / 150247, which is incorporated by reference in its entirety.

[0083] Additional details regarding various components of the steam cracking equipment and process can be found in International Patent Application Publication No. WO 2020 / 150244, which is incorporated by reference in its entirety.

[0084] The above description and examples provide a complete description of the structure and use of exemplary embodiments. Although some embodiments have been described above to a certain extent or with reference to one or more separate embodiments, those skilled in the art may make many changes to the disclosed embodiments without departing from the scope of the invention. Therefore, the different illustrative embodiments of the apparatus of the present invention are not intended to be limited to the specific forms disclosed. On the contrary, they include all modifications and substitutions that fall within the scope of the claims, and embodiments other than the embodiments shown may include some or all of the features of the depicted embodiments. For example, components may be combined into an integral structure, and / or connections may be replaced. In addition, where appropriate, aspects of any of the examples described above may be combined with aspects of any other examples described to form additional examples having comparable or different characteristics and solving the same or different problems. Similarly, it will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments.

[0085] The claims are not intended to include, and should not be interpreted as including, means-plus-function or step-plus-function limitations unless such limitations are explicitly recited in a given claim using the phrase “means for” or “step for” respectively.

Claims

1. An electric furnace for a chemical production process, said furnace comprising: a primary heating section comprising a heater housing having a first end, a second end, and first and second furnace sidewalls extending from the first end to the second end; a radiant heat exchanger section comprising an exchanger housing having an exchanger first end, an exchanger second end, and first and second exchanger sidewalls extending from the exchanger first end to the exchanger second end; a plurality of electrically conductive reactor tubes extending through the heater housing and the exchanger housing, each of the reactor tubes defining a flow path from an inlet end of the reactor tube to an outlet end of the reactor tube, each of the inlet and outlet ends having a flanged connector; an electrical circuit configured to electrically connect the longitudinal sections of each of the reactor tubes in series such that application of a voltage differential between a first end of the longitudinal section of a first one of the reactor tubes and a second end of the longitudinal section of a last one of the reactor tubes causes current to flow sequentially through the longitudinal sections of all of the plurality of reactor tubes, wherein at least a majority of the longitudinal sections are disposed in the heater housing; wherein the radiant heat exchanger section is configured to, for each of the reactor tubes, reduce the temperature of an outlet end of the tube relative to a nearest first or second end of a longitudinal portion of the tube by arranging flow within adjacent reactor tubes to be in alternating directions or by defining at least one channel between an inner wall and at least one of the first exchanger side wall or the second exchanger side wall, the channel being operable to absorb thermal energy from the reactor tube through the inner wall.

2. The furnace of claim 1, wherein the inlet end of the reactor tube is disposed on the first end of the heater housing, and the outlet end of the reactor tube is disposed on the second end of the exchanger housing.

3. The furnace of claim 1 , wherein the inlet and outlet ends of the reactor tubes are disposed on the second end of the exchanger housing, and each reactor tube includes a U-shaped portion at the first end of the heater housing.

4. The furnace of claim 1 , wherein the plurality of reactor tubes comprises a first subset of reactor tubes disposed with their inlet ends on the first end of the heater housing and their outlet ends on the second end of the exchanger housing, and a second subset of reactor tubes disposed with their outlet ends on the first end of the heater housing and their inlet ends on the second end of the exchanger housing.

5. The furnace of any one of claims 1 to 4, wherein the electrical circuit connects the second end of the longitudinal section of the first one of the reactor tubes to the first end of the longitudinal section of the second one of the reactor tubes, and connects the second end of the longitudinal section of the second one of the reactor tubes to the first end of the longitudinal section of the third one of the reactor tubes.

6. The furnace according to any one of claims 1 to 5, wherein: (a) the first exchanger sidewall defines a channel configured to receive a fluid to absorb thermal energy from the first exchanger sidewall; (b) the second exchanger sidewall defines a channel configured to receive a fluid to absorb thermal energy from the second exchanger sidewall; or (c) both (a) and (b).

7. The furnace of claim 6, wherein the outlet of each channel is fluidly coupled to a steam drum.

8. The furnace of any one of claims 1-7, further comprising a catalyst disposed in the reactor tube, wherein the catalyst is a steam reforming catalyst configured to react steam and methane gas to form hydrogen and carbon monoxide.

9. The furnace according to any one of claims 1 to 8, wherein: (a) the outlet ends of the reactor tubes are coupled to a conductive collection manifold, and wherein the reactor tubes are electrically isolated from the collection manifold; (b) the inlet ends of the reactor tubes are coupled to a conductive feed manifold, and wherein the reactor tubes are electrically isolated from the feed manifold; or (c) both (a) and (b).

10. The furnace of claim 8, wherein electrical isolation of each reactor tube is provided by one or more flanged pipe isolation joints (PIJs).

11. A method comprising: heating a feedstock using the furnace of any one of claims 1 to 10 by applying a voltage difference between a first end of a longitudinal section of a first one of the reactor tubes and a rearmost end of a longitudinal section of a second one of the reactor tubes to cause current to flow sequentially through the longitudinal sections of all of the plurality of reactor tubes; wherein the voltage difference is greater than 100 volts (V); and wherein the current does not flow into either the collection manifold or the feed manifold.

12. The method of claim 11, wherein the furnace is part of a steam methane reformer system and the feedstock comprises steam and methane.

13. The method of claim 11, wherein the furnace is part of a steam cracking system and the feedstock comprises steam and at least one component selected from the following list of components: naphtha, liquefied petroleum gas, and ethane.

14. The method of claim 11, wherein (a) the first exchanger sidewall defines a channel configured to receive a fluid to absorb thermal energy from the first exchanger sidewall; (b) the second exchanger sidewall defines a channel configured to receive a fluid to absorb thermal energy from the second exchanger sidewall; or (c) both (a) and (b), and wherein the outlet of each channel is coupled to a steam drum in a fluidic manner.

15. The method according to claim 14, further comprising: H2O is caused to flow through the channels of the exchanger sidewalls to absorb heat energy from the exchanger sidewalls.

16. The method according to claim 15, further comprising: The H2O is sent from the channels in the sidewall of the exchanger to the steam drum to separate liquid and steam from the H2O.

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